The goal of this project is to directly determine whether Chlamydia specific secretory IgA (sIgA) plays a role in protection from, or resolution of, chlamydial infection of the mouse genital tract. In order to address this question we will 1) produce murine hybridomas that secrete polymeric IgA (pIgA) monoclonal antibodies (mAbs) specific to chlamydial surface components, and 2) determine their ability to protect against chlamydial genital tract infection in a murine model. mAbs will be administered to naive animals by subcutaneously implanting a mAb secreting hybridoma in the backs of syngeneic mice (backpack tumor system). This approach is made possible by the fact that systemically delivered pIgA is specifically complexed with secretory piece and transported to mucosal surfaces as sIgA, whereas monomeric IgA (mIgA) and IgG are not. To date, three murine hybridomas have been generated that produce pIgA specific for the surface of Chlamydia trachomatis MoPn. These hybridomas resulted from fusion experiments using mesenteric lymph node derived lymphocyte populations that were enriched for IgA surface positive cells. Using pIgA and IgG secreting hybridomas, we are currently conducting a pilot experiment to characterize the backpack tumor system in our laboratory. Preliminary data indicate that the take rate for tumor development is >80%, that high levels of mAb are produced by such tumors, and that tumor growth rates vary significantly between tumor cell lines. With this information, we can now evaluate the role of anti-chlamydial sIgA in protection against chlamydial colonization of the genital tract mucosae as well as its role in resolving established infections of the genital tract. The same collection of mAbs will allow for future studies that compare in vivo protection with in vitro neutralization of chlamydial infectivity, as well as, investigations of mucosae specific IgA antibody dependent cellular cytotoxicity as a potential mechanism of protective immunity.